Influence of fiber coating and polymer modification on mechanical and thermal properties of bast/basalt reinforced polypropylene hybrid composites

Natural fibers, such as kenaf, hemp, and flax, also known as bast fibers, offer several benefits such as low density, carbon dioxide neutrality, and less dependence on petroleum sources. Their function as reinforcement in polymer composites offers a great potential to replace a segment of the glass fiber-reinforced polymer composites, especially in automotive components. Despite their promising benefits, they cannot meet the structural and durability demands of automobile parts because of their poor mechanical properties compared to glass fibers. The focus of this research work was the improvement of the mechanical property profile of the bast fiber reinforced polypropylene composites by hybridization with natural high-performance basalt fibers and the influence of basalt fibers coating and polymer modification at the mechanical and thermal properties of the composites. The specific tensile strength of the composite with polymer tailored coating was 39% and the flexural strength was 44% higher than the composite with epoxy-based basalt fibers. The mechanical performance was even better when the bast/basalt hybridization was done in maleic anhydride modified polymer. This led to the conclusion that basalt fibers sizing and polymer modification are the deciding factors in defining the optimal mechanical performance of the composites by influencing the fiber-matrix interaction. The composites were analyzed for their mechanical, thermal, and morphological properties. The comparison of bast/basalt hybrid composite with bast/glass fibers hybrid composite showed a 32% higher specific flexural and tensile strength of the basalt hybrid composite, supporting the concept of basalt fibers as a natural alternative of the glass fibers.